Abstract: To establish the sublethal concentrations domain, acute and chronic oral tests were
conducted on caged honeybee workers (Apis mellifera L) using imidacloprid and a metabolite, 5-OHimidacloprid,
under laboratory conditions. The latter showed a 48-h oral LD50 value (153ng per bee)
five times higher than that of imidacloprid (30ng per bee). Chronic feeding tests indicated that the
lowest observed effect concentrations (LOEC) of imidacloprid and of 5-OH-imidacloprid on mortality

Although sublethal dosages of insecticide to nontarget insects have never been an important issue, they are attracting more and more attention lately. It has been demonstrated that low dosages of the neonicotinoid insecticide imidacloprid may affect honey bee, Apis mellifera L., behavior. In this article, the foraging behavior of the honey bee workers was investigated to show the effects of imidacloprid. By measuring the time interval between two visits at the same feeding site, we found that the normal foraging interval of honey bee workers was within 300 s. However, these honey bee workers delayed their return visit for >300 s when they were treated orally with sugar water containing imidacloprid. This time delay in their return visit is concentration-dependent, and the lowest effective concentration was found to be 50 μg/liter. When bees were treated with an imidacloprid concentration higher than 1,200 μg/liter, they showed abnormalities in revisiting the feeding site. Some of them went missing, and some were present again at the feeding site the next day. Returning bees also showed delay in their return trips. Our results demonstrated that sublethal dosages of imidacloprid were able to affect foraging behavior of honey bees.

Figure 4: The ratio of missing bees after feeding on 50% sugar water containing different concentrations of imidacloprid.

ABSTRACT
Groundwater contamination risk indices are presented for 106 pesticides currently applied on two widespread cultivations in the Province of Ferrara, sugar-beet and pear-tree. The indices were evaluated on the basis of the Attenuation Factor (Rao, 1985), for six soils representative of the pedological regions of the area under study.

Aiming to evaluate the contamination of groundwater by pesticides in cotton growing areas, an SPE-based method (styrene-divinylbenzene copolymer - SDVB) was developed for the simultaneous determination of twelve pesticides in water by HPLC/DAD. The method was validated and average recoveries ranged from 73 to 113%, with a relative standard deviation of 2 to 16%. Detection limits ranged from 0.06 to 0.57 μg L-1. The method was applied to groundwater samples (110) from cotton fields located in “Primavera do Leste”, Mato Grosso state, Brazil.

This document reviews all routes of environmental fate for imidacloprid under field conditions for its potential use in controlling the glassy-winged sharpshooter. Imidacloprid is a chloronicotinoid insecticide.

The procedure to assess the risk posed by systemic insecticides to honey bees follows the European Directives and depends on the determination of the Hazard Quotient (HQ), though this parameter is not adapted to these molecules. This paper describes a new approach to assess more specifically the risk posed by systemic insecticides to honey bees with the example of imidacloprid (Gaucho). This approach is based on the new and existing chemical substances Directive in which levels of exposure (PEC, Predicted Exposure Concentration) and toxicity (PNEC, Predicted No Effect Concentration) are compared. PECs are determined for different categories of honey bees in relation to the amounts of contaminated pollen and nectar they might consume. PNECs are calculated from data on acute, chronic, and sublethal toxicities of imidacloprid to honey bees, to which selected assessment factors are applied. Results highlight a risk for all categories of honey bees, in particular for hive bees. These data are discussed in the light of field observations made on honey bee mortalities and disappearances. New perspectives are given to better determine the risk posed by systemic insecticides to honey bees.

Following evidence for the intoxication of bees, the systemic insecticide imidacloprid was suspected
from the mid nineties of having harmful effects. Recently, some studies have demonstrated that
imidacloprid is toxic for the bees at sub-lethal doses. These doses are evaluated in the range between
1 and 20 μg kg–1, or less. It appeared thus necessary to study the fate of imidacloprid in the environment
at such low levels. Thus, we developed methods for the determination of low amounts, in
the μg kg–1 range, of the insecticide imidacloprid in soils, plants and pollens using high pressure liquid
chromatography – tandem mass spectrometry (LC/APCI/MS/MS). The extraction and separation
methods were performed according to quality assurance criteria, good laboratory practices and the
European Community’s criteria applicable to banned substances (directive 96/23 EC). The linear concentration
range of application was 1–50 μg kg–1 of imidacloprid, with a relative standard deviation of
2.9% at 1 μg kg–1. The limit of detection and quantification are respectively LOD = 0.1 μg kg–1 and
LOQ = 1 μg kg–1 and are suited to the sub-lethal dose range. This technique allows the unambiguous
identification and quantification of imidacloprid. The results show the remanence of the insecticide in
soils, its ascent into plants during flowering and its bioavailability in pollens.
Key words: imidacloprid, insecticide, Gaucho®, analysis, soils, plants, pollens, bees

"I would draw your attention to this quote, from the label of Premise 75, a Bayer product with 75% imidacloprid and 25% inert used to kill termites and ants (other social insects like bees): "Premise causes a range of effects in termites, they stop feeding and are unable to maintain their colony. A second effect, exclusive to Premise, is called Premise plus Nature. This product makes termites susceptible to infection by naturally occurring organisms. Either way, the termites die and your home is protected". Exactly, my point, weaken the colony of bees with lethal and sublethal effects and surely disease will set in, and it is crass to use this effect to advertise a product, and then use it to blame beekeepers' problems on diseases."

These comments, submitted by the National Honey Bee Advisory Board to EPA concerning the registration of imidacloprid, a systemic pesticide produced by Bayer Chemical Company, have been edited here because of length. But the stories have not been changed or altered. The NHBAB consists of beekeepers from both the AHPA and the ABF, and represents most of the nation’s commercial beekeepers. EPA now must act on these and other comments regarding this compound. At the same time, this group of beekeepers and Bayer are meeting to discuss continued research with this compound. Time will tell if increased regulation, or more precise research improve the situation.

Beekeepers from around the United States, and around the world, have had persistent problems associated with the use of the systemic pesticide imidacloprid. Since the first uses of imidacloprid in France in 1994 on sunflowers beekeepers reported problems. Soon the condition was given a name in France: “mad bee disease.” Problems reported by beekeepers, combined with mounting independent scientific data, caused the French Minister of Agriculture to suspend the use of imidacloprid on sunflowers in January of 1999. In February 2004, France extended the suspension to include uses on corn. At the same time they further broadened the ban on systemic insecticides to include the chemical fipronil.